Reverse circulation rotary expansible drill bits



Oct. 22, 1968 A. W. KAMMERER, J 3,406,769

REVERSE CIRCULATION ROTARY EXPANSIBLE DRILL BITS 7 A s s Filed OCT'. 24,1966 Oct. 22, E968 A. W. KAMMERER, ,m 3,406,769

REVERSE CIRCULATION ROTARY EXPANSIBLE DRILL BITS 2 f F @4% w Q w M@ w..

IN veA/T012 2 Sheets-Sheet 2 @Jeez/E@ MC a lOl veA/ey.-

ters expanded outwardly.

United States Patentl O ABSTRACT OF THE DISCLOSURE A rotary drill bitfor use in a well bore and having cutters expandable outwardly inresponse to fluid pressure in the well bore annulus surrounding thedrill string, the cuttings passing upwardly through the the top of thewell bore. i

l The present invention relates to rotary `drill bits, and moreparticularly to rotary drill bits of the expansible type `capableofdrilling a ,bore hole of enlarged diameter, of

enlarging a borehole below a string of casing to a greater diameter thanthe inside diameter of the casing through which the drill bits arecapable of passing, or of severing and milling away a section of wellcasing located in the bore hole. 4 d

Certain bore holes are drilled in formations by reversely circulatingthe drilling iiuid; that iS, the drilling fluid is pumped down the borehole through the annular space surrounding the string of drill pipe tothe drilling region, to ilush the cuttings from such region and upwardlythrough the drill bit and drill pipe to the top of the hole `or drillingrig. An object of the present invention is t provide rotary drill bitsof the expansible type, in which the circulating fluid pumped downwardlythrough the annulus around the drill pipe string effects outwardexpansion of the drill bit cutters, such cutters bein-g of the type todrill the formation, or of the type to mill away a casing section. v 1 KAnother object of the invention is to provide a rotary drill bit havingcutters expandable outwardly by the pressure of fluid reverselycirculated within the bore hole, in which the cutters are retained intheir, fully outwardly expanded position despite cessation in thecirculation of fluid through the bore hole. More specifically, theapplication of drilling weight to the drill bit retains the cut- Thisinvention possesses many other advantages, and has other objects whichmay be made more clearly apparent from a consideration of several formsin which it may be embodied. Such forms are shown inthe drawingsaccompanying and forming part of the present specification. These formswill now be described in detail for the purpose of illustrating thegeneral principles of the invention; but it is to be understood thatsuch detailed description is not to be taken in a limiting sense, sincethe scope of the invention is best deiined by the appended claims.

Referring to the drawings:

FIGURE 1 is a longitudinal section through a rotary expansible drill bitdisposed within a bore hole, with the cutters and other parts occupyinga retracted position;

FIG. 2 is a longitudinal section similar to FIG. 1, disclosing therelative position of the parts of the drill bit with its cutters intheir fully expanded position;

FIG. 3 is a longitudinal section through another speciiic rotaryexpansible drill bit disposed in a well bore, and with its cutters andother parts occupying a retracted position;

FIG. 4 is a view similar to FIG. 3 disclosing the relative positions ofparts of the bit with the cutters in their outwardly expanded position.

drill string toward Y As shown in the drawings, a rotary expansibledrill bit A is secured to the lower end of a string of drill pipe Bextending to the top of a bore hole C, and by means of which the drillbit is lowered through the bore hole to a location therein at which itsdiameter is to be enlarged. In the form of invention, illustrated inFIGS. l and 2, the upper portion of the rotary drill bit consists of amandrel 10 having an upper pin'114 threadedly connected to the lower endof the string of drill pipe B. This mandrel includes an upper kelly ordrill lstern member 12 slidably splinedto the main body 13 of the drillbit. The exterior 14 of the lower portio'npof the kelly is non-circularin Ishape, being telescopically received in a companionnoncircularsocket 15 formed in the main bit body' 13. vAs an Vexar'nple,'the kellyexterior 14 and the socket 15 maybe of hexagonal shape to enable thekelly 12 to be moved `longitudinally with respect to the body, whilestill being capable of transmitting rotary motionto the body 13.

The body 13 has alimited range of longitudinal relatife movement alongthe mandrel 10, its upward movement being determined by engagement of aninwardly directed body shoulder 16 with the lower end 17 of the kelly,and its downward movement being limited by engagement of a stop device18, secured within the upper portion of the body, with a pistonstructure 19 secured to the mandrel. As specifically shown in thedrawings, the piston structure includes an annular piston 20encompassing the cylindrical portion 21 of the kelly of the mandrelsubstantially above its hexagonal portion 14, the lower end of thepiston resting upon a lower split, snap retainer ring 22 located ina'peripheral groove 23 in the kelly, its upper end engaging an outwardlydirected flange portion 24 of a two-piece retainer` ring 25 disposed ina peripheral groove 26 in the mandrel, the piston 20 encompassing thetwo-piece upper retainer ring below its flange 24. Leakage of fluidbetween the kelly 12 and piston 20 is prevented by a suitable side sealring 27 on'the kelly engaging the inner surface of the piston 20, vthepiston having a suitable piston ring 28 mounted thereon slidably sealingagainst the inner cylindrical wall 29 of the drill bit body, which wallextends upwardly from a shoulder 30 marking the upper vend ot thenon-circular body socket 15.

The upper stop device 18 includes a stop ring 31 insert able downwardlywithin an upper body counterbore 32 and bearing against an upwardlydirected body shoulder 33, this stop ring 31 extending across thetwo-piece retainer ring 25 and being held in a downward position vagainst the body shoulder by one or a plurality of split,

When the body 13 is disposed in a downward position with respect to thelmandrel 10, as disclosed in FIG. 1, the upper stop ring 31 may restupon the two-piece retainer ring 25. At this time, a lower cylinder head36, secured within the body 13 and which surrounds the upper Ikelly ordrill stem member 12, is spaced substantially below the piston structure19. This cylinder head 36 is annular in shape, being secured to the bodyby a plurality of circumferentially spaced screws 37 threaded in thebody and extending into a peripheral groove 38 in the cylinder head. Thecylinder head has an inner seal ring 39 slidably and sealingly engagingthe cylindrical periphery 21 of the kelly above its hexagonal portion14, and also an external seal ring 40 sealing against the innercylindrical wall 29 of the cylinder portion 41 of the main body 13 ofthe drill bit.

The -body 13 has a plurality of expansible parts mounted on it. Theseinclude cutter supporting members 42 pivotally mounted in one or morebody slots 43 on hinge pins 44 which are suitably secured to the body toprevent loss therefrom. Each cutter supporting member depends from thehinge pin and carries a suitable cutter 45 onfits lower end. Asspecifically illustrated, the cutters 45 are of the toothed l'rollertype, beingV designed for drilling upon relatively hard formations.However, the cutters could be constituted as drag cutters, or asmilling1 cutters, in the event the e-xpansible drill -bit is to beemployed for severing and milling away a section of well casing or fordrilling a soft formation.

The cutter supporting members 42 and the cutters 45 themselves tend tooccupy a retracted position substantially entirely within the continesof the main body 13 of the bit. These cutter supporting members and thecutter structures are expandable outwardly to enlarge the diameter of anexisting bore hole, or, if milling cutters are employed, to sever andmill away a length of casing disposed in the bore hole. To accomplishthe expansion, each cutter supporting member 42 has an inclined expandersurface 46 on its inner portion below its hinge pin 44, which tapers ina downward and inward direction, each expander surface terminating in alock surface 47 formed on a lock portion 48 of the cutter supportingmember. The outward expansion is accomplished by relatively elevatingthe body 13 along the mandrel 10, as described specically hereinbelow.which will produce relative longitudinal movement between the cuttersupporting members 42 and the tubular member 49 of the mandrel 10. Thistubular member includes a lower portion 50 slidable within a guidebushing 51 `mounted in a bridge 52 secured to the body and extendingacross the body slot or slots 43. The guide bushing 51 is disposed belowthe lock portions 48 of the cutter supporting members 42 and is securedin place by a lower contractible split retainer ring 53 disposed in agroove 54 in the bushing and engaging the lower end of the bridge 52, anupper flange 55 on the bushing engaging the upper end of the bridge.

Located initially substantially above the guide bushing 51 and below thehinge pins 44, and in cutter supporting member recesses 56, is a mandrellock and expander 57 which has outer surfaces 58 adapted to engage theexpander surfaces 46 and the lock surfaces 47. The lock and expander maybe formed integral with the tubular member 49, the upper portion 90 ofthe latter being piloted within a socket 91 formed in the lower portionof the kelly. This upper portion 90 is in enlarged boss engaging adownwardly facing shoulder 60 of the kelly, the tubular member beingheld against the shoulder by a suitable split retainer or lock ring 61expanded into an internal groove 62 encompassing the kelly socket 91 andengaging the lower end of the tubular member boss 90.

As described hereinbelow, a suitable tiuid medium is provided, which ispumped downwardly in the bore hole around the exterior of the drillstring B, such tiuid passing around the exterior of the drill bit A tothe drilling region to flush the cuttings inwardly through the slot orslots 43 of the body and toward a flow bean 65 mounted within acounterbore 66 in the lower end of the tubular member 49, the tiuidpassing upwardly through the central orifice or passage 67 of the owbean and through the central passage 68 of the tubular member 49 intothe central passage 69 through the kelly 12, from where the fluid andcuttings pass upwardly through the drill pipe string B to the top of thebore hole. The iiuid can also pass through the slots 43 around theexterior of the mandrel and into the hexagonal portion 15 of the body13, leakage of this fluid upwardly around the tubular member yboss 58being prevented by a suitable seal ring 70 in the upper kelly sealinglyengaging the periphery of the enlarged boss.

Assuming the'body 13 of the tool to be elevated relatively along thetubular mandrel 10, the inclined expander surfaces 46 of the cuttersupporting members shift upwardly along the lock and expander portion 57of the tubular member 49. During such upward shifting, the cuttersupporting members 42 and the cutters 45 carried thereby will pivotabout the hinge pins 44 and be urged in an outward direction. The upwardmovement of the body 13 with respect to the mandrel can continue untilthe cutters 45 have been shifted outwardly to their fullest extent, asdetermined by engagement of stop shoulder 71 on the cutter supportingmembers with companion shoulders 72 formed in the body 13 on oppositesides of the body slot or slots 43. When such expansion occurs, the bodyshoulder 16 will engage the lower end 17 of the kelly portion 12 of thetubular mandrel 1t), and the lock and expander 57 on the tubular memberwill be disposed 4behind and in engagement with the lock portions 48 ofthe cutter supporting members 42.

The relative upward movement of the body 13 of the tool along thetubular mandrel 10 is accomplished by the action of fluid pressure beingpumped downwardly through the annulus D surrounding the drill pipestring B. This pressure will be greater than the pressure within thepassages 68, 69 of the tubular mandrel 10, in view of the pressure dropoccasioned by the orifice 67 formed in the lower bean 65 secured withinthe tubular member 49. The pressure within the central passage 69 willbe the same pressure as exist in the cylinder space 75 defined betweenthe lower cylinder head 36 and piston 20, and between the periphery 21of the kelly portion 12 of the mandrel and the inner wall 29 of thecylindrical portion 41 of the main body of the drill bit, communicationbetween the central passage 69 and the annular cylinder space 75 beingprovided by bleeder ports 76 in the kelly extending between the centralpassage and the annular cylinder space immediately below the pistonstructure.

The cylinder head 36 itself is subject to the relatively high pressureof the fluid surrounding the bit body 13, and which is capable ofpassing upwardly through the slots 43 and around the kelly portion 12 ofthe body for action in an upward direction on the cylinder head 36 overthe annular area R. Thus, the cylinder head 36 is subject to therelatively high pressure of tiuid acting upon it in an upward direction;whereas, the pressure of the uid in the cylinder space 75 above thecylinder head is at a relatively low pressure, a pressure differentialbeing provided which is capable of shifting the body 13 upwardly alongthe mandrel 10 until the cutters 45 have been expanded outwardly totheir fullest extent, as disclosed in FIG. 2. The fluid under pressure,as has been noted above, is developed by restricting the ow of fluidthrough the orifice 67 of the mandrel. As a result of such restrictionof flow, the pumping of a compressed gas or drilling mud at an adequaterate downwardly through the annulus D around the drill pipe and aroundthe drill bit A will result in a relatively high pressure of iiuid beingpresent in the well bore for upward action on the cylinder head 36surrounding the exterior of the kelly 12.

The tluid pressure in the annulus D is also acting in a downwarddirection upon the piston structure 19, and will force, or tend toforce, the mandrel 10 downwardly within the body 13 and shift theexpander 57 down along the surfaces 46 to expand the cutters 45outwardly. Such action can occur upon contact of the cutters against thewall of the hole C, which resist upward movement of the cutters and bodyalong the wall of the hole, the drill pipe B stretching downwardly orelongating, or the drill pipe being slacked ott sufiiciently at the topof the wall bore, to permit its lowering for the purpose of enabling themandrel 10 to lower within the body 13 and along the supporting members42.

In the use of the apparatus disclosed in FIGS. 1 and 2, the cutters 45are initially in their retracted position, as disclosed in FIG. 1, thebody 13 of the tool and the cutter members being located in theirinitial lower position with respect to the mandrel 10. The drill bit Ais lowered on a string of drill pipe B to the desired location in thewell bore at which the cutters are to be expanded outwardly. When suchposition is reached, the drilling uid is pumped downwardly through theannulus D sur- J rounding the string of drill pipe B, passing upwardlythrough the orifice 67 and developing a back pressure below the cylinderhead 36, which will shift the |body 13 and cutters 45 upwardly along themandrel 10. During such upward shifting, the drill pipe and bit A arerotated at the proper speed, the cutter supporting members 42 shiftingupwardly along the mandrel lock and expander 57 and progressivelyenlarging the well bore, until the cutters 45 have been expanded totheir fullest extent, as determined by engagement of the body shoulder16 with the lower end 17 of the kelly, and the engagement of the stopshoulders 71 on the cutter supporting members with the companionshoulders 72 formed in the body on opposite sides of its slot or slots.

Appropriate drilling weight can now be imposed downwardly through thedrill pipe string B on the drill Bit A, which will be transmitteddirectly from the kelly 12 to Vthe body `13 of the tool, and through itsshoulders 72 to the cutter supporting members 42 and to the cutters 45,the cutters being urged against the transverse shoulder E produced inthe formation by the expanded cutters. The rotation of the drill pipestring and drill bit continues with the circulating or drilling fluidbeing pumped down through the -annulus D, such duid passing around theexpanded cutters 45 to cool them and clean them of cuttings, and tocarry the cuttings inwardly toward the orilice 67 and upwardlytherethrough into the passages 68, 69 through the mandrel 10, and thenupwardly through the drill pipe string B to the top of the bore hole orto the top of the drilling rig. Because of the relatively smallcross-sectional area through the drill pipe B, as compared to thediameter of the enlarged well bore F, the cuttings will be conveyed bythe drilling fluid at relatively high velocities through the drill pipeto the top of the latter. This becomes of importance in the event that agreatly `enlarged bore F is drilled by the cutters, since thecirculation of uid in the normal direction, that is, downwardly throughthe drill pipe B and upwardly around the drill bit A and through theannulus D `surrounding the string of drill pipe, would result in arather low velocity of fluid passing upwardly through the annulus, suchvelocity oftentimes being insufficient to carry the cuttings upwardly tothe t-op of the bore hole.

When the enlarged bore hole F has been produced to the desired length,or upon the cutters 45 becoming dull, the drill bit can be removedsimply by ceasing the circulation of fluid downwardly through theannulus D surrounding the drill pipe, 4and by elevating the string ofdrill pipe, which will elevate the mandrel within the body 13 of thetool, and replace the mandrel lock and expander 57 above the locksurfaces 47 and within the cutter member recesses 56, the pistonstructure 19 engaging the stop ring 31 to raise the body 13 of the tool.The cutter supporting members 42 and cutters 45 are then free to shiftinwardly back substantially within the confines of the `body 13 of thetool, allowing the entire drill bit A to be elevated in the bore hole tothe top thereof, or to the drilling rig. In the event the cutters 45 donot shift inwardly by gravity upon elevation of the mandrel 10 withinthe body 13 ofthe tool, such elevation will cause a shoulder 80 on thetubular member 49 to engage the inwardly extending fingers 81 on thecutter supporting members 42 and swing them upwardly, -causing thecutter supporting members and cutters below the hinge pins 42 to swinginwardly back within the confines of the drill bit body 13, permittingthe string of drill pipe B, with the drill bit A thereon, to be elevatedwithin the bore hole and removed entirely therefrom.

In the vform of invention illustrated in FIGS. 3 and 4, the string ofdrill pipe B is connected directly to the main body 13a of the drillbit, and the mandrel 10a is shifted downwardly hydraulically by thepressure of fluid surrounding the main body to expand the cuttersupporting members 42 and cutters 45 outwardly. The mounting of thecutter supporting members and cutters in the main body 13a and thecoaction -between the mandrel 10a, and particularly its expander andlock 57 and the cutter supporting members 42 to effect outward expansionof the latter, is substantially the same as in the form of inventiondisclosed in FIGS. 1 and 2.

The main body 13a is elongate, including a lower cylinder head above theupper end of its slot or slots 43, extending inwardly toward the mandrelor plunger 10a above the mandrel lock and expander 57, and having asuitable rod seal 101 slidably and sealingly engaging the periphery ofthe lower rod portion 49a of the mandrel or plunger, which extendsupwardly within a cylinder 41a formed by the upper portion of the bodyof the tool. This cylinder includes an upper cylinder head 102threadedly secured to the upper cylindrical sleeve portion of thecylinder 41a, and having a threaded pin 103 threadedly secured to thelower end of the drill pipe string B. The mandrel 10a has a piston` 104slidable along the Vinner cylindrical wall 105 of the cylinder, therebeing a suitable piston seal ring 106 mounted thereon for sealingagainst the cylinder wall. The mandrel `10a further includes an upperrod portion 107 extending upwardly from the piston 104 and slidablewithin a central bore 103 extending through the upper cylinder head 102,there being a suitable rod seal 109 on the upper head slidably andsealingly engaging the upper rod portion.

Initially, the mandrel 10a is retained in an upward position within thebody by a helical compression return spring 110 disposed in a lowpressure cylinder space 111 provided between the piston 104 and lowercylinder head 100, the lower end ofthe spring bearing against the lowercylinder head, and its upper end against the piston and urging thepiston upwardly, and consequently the mandrel or plunger 10a upwardly toa position in which the cutter supporting members 42 and cutters 45 areretracted, the piston being spaced a short distance below the uppercylinder head 102. The mandrel is urged downwardly within the cylinderand body of the tool by fluid under pressure in the annular space Dsurrounding the drill pipe and the body of the tool. Such fluid underpressure passes through inlet ports 111a in the upper portion of thecylinder skirt into a high pressure cylinder space 112 between the uppercylinder head 102 and the piston 104, urging the piston 104 downwardlyagainst the force of the return spring 110, and the entire mandrel 10adownwardly to shift the expander and lock 57 downwardly along theexpander surfaces 56 of the cutter supporting members 42 to expand thecutters 45 outwardly, the mandrel moving downwardly until the expanderand lock 57 engages the upper end of the guide bushing 51, at which timethe expander and lock is disposed behind the lock surfaces 47 on thecutter supporting members, as disclosed in FIG. 4. Fluid within the lowpressure cylinder space 111 can pass through the bleeder ports 76a inthe lower rod portion 49a of the mandrel into the central passage 69athrough the mandrel, which opens upwardly into the cylinder head 102 andthe string of drill pipe B, the lower portion of the central mandrelpassage communieating with the body slots 43 through the orifice or theow restricting bean 65 mounted within the lower end of the mandrel 10a.

In the use of the particular expansible drill bit disclosed in FIGS. 3and 4, the parts initially occupy the relative positions illustrated inFIG. 3, the return spring 110 tending to retain the mandrel 10a in itsupper position within the body 13a, the cutters 45 and cutter supportingmembers 42 being retracted substantially completely within the confinesof the body. The apparatus is lowered on the drill pipe B in the borehole C to a location in which the cutters 45 are to be expandedoutwardly, and the drill bit is then rotated by rotating the string ofdrill pipe, while circulating fluid is pumped downwardly through theannullus D surrounding the drill pipe. The fluid will pass upwardlythrough the orice 67 into the central passage 69a through the mandrel,the pressure in the low pressure cylinder space 111 then being less thanthe pressure in the high pressure cylinder space 112, the high pressurefluid passing through the inlet ports 111a into the upper cylinder space112 and acting downwardly on the piston over its annular area S, asshown in FIG. 4, shifting the mandrel 10a downwardly and causing theexpander and lock portion 57 of the mandrel to engage the expandersurfaces 46 on the cutter supporting members 42, to shift them outwardlyand to force the cutters 45 against the wall of the bore hole C.

The cuttings produced by the cutters are flushed by the circulatingfluid inwardly through the body slots 43 and upwardly through the bean65 into the central passage 69a, where they will flow upwardly throughthe drill pipe B to the top of the bore hole or drilling rig. Thedownward force of the fluid on the piston 104 and the mandrelprogressively shifts the cutters 45 outwardly to a greater extent,forcing them against the wall of the well bore, until the cutters havebeen expanded outwardly to their maximum extent, as determined byengagement of the shoulders 71 on the supporting members with thecompanion body shoulders 72 on opposite sides of its slots 43.

Rotation of the drill pipe B can now continue while appropriate drillingweight is imposed thereby upon the body 13a of the tool and the cutters45, forcing the cuters against the annular shoulder E which they form inthe bore hole between the enlarged bore diameter F and the original borehole diameter C, the cutters acting upon the shoulder E to drill itaway, and the cuttings continually being flushed by wardly through theannulus D around the drill pipe, and around the drill bit A, inwardlytoward its axis and upwardly through the mandrel 10a into the drill pipeB to be conveyed to the surface.

After the hole enlarging operation has been completed, or the cutters 45become dull, circulation of fluid is discontinued which will reduce thepressure in the high pressure cylinder space 112 and allow the spring110 to shift the mandrel or plunger 10a upwardly to its initial positiondisclosed in FIG. 3, the expander and lock 57 being again located withinthe supporting member recesses 56, the cutters 45 shifting inwardlywithin the confines of the body. If the cutters do not move inwardly oftheir own accord, then the shoulder 80 on the mandrel 10a will engagethe inwardly directed fingers 81 on the upper portions of the cuttersupporting members 42 and swing them upwardly about their hinge pins 44,and the pendent portions of the cutter supporting members and cuttersinwardly substantially entirely within the confines of the bit body. Thedrill bit A can now be elevated in the bore hole by elevating the stringof drill pipe B, and removed entirely from the bore hole.

I claim:

1. In a rotary drill bit adapted for attachment to a drill string to berotated thereby in a bore hole: a main body; cutter means carried bysaid body; and means engaging said cutter means and responsive to fluidpressure in the bore hole annulus surrounding the `drill string forexpanding said cutter means laterally outwardly of said body.

2. In a rotary drill bit as defined in claim 1; said expanding means forsaid cutter means comprising a mandrel movable longitudinally Within andrelative to said body, said body and mandrel providing cylinder andpiston means having high pressure areas subject to the fluid underpressure in the bore hole annulus to effect expansion of said cuttermeans.

3. In a rotary drill bit as defined in claim 1; said expanding means forsaid cutter means comprising a mandrel movable longitudinally within andrelative to said body, said body and mandrel providing cylinder andpiston means having high pressure areas subject to the fluid underpressure in the bore hole annulus to effect expansion of said cuttermeans; said mandrel having a passage the drilling fluid pumped down- '8through which fluid pumped down the bore hole annulus can flow upwardlyand into the drill string.

4. In a rotary drill bit as defined in claim 1; said expanding means forsaid cutter means comprising a mandrel movable longitudinally within andrelative to said body, said body and mandrel providing cylinder andpiston means having high pressure areas subject to the fluid underpressure in the bore hole annulus to effect expansion of said cuttermeans; said mandrel having a passage through which fluid pumped down thebore hole annulus can flow upwardly and into the drill string; means forreducing the pressure of the fluid flowing upwardly through the mandrelpassage; and means communicating the low pressure area of said cylinderand piston means with the reduced pressure region of said mandrelpassage.

5. In a rotary drill bit as defined in claim 1; said expanding means forsaid cutter means comprising a mandrel movable longitudinally within andrelative to said body, said body and mandrel providing cylinder andpiston means having high pressure areas subject to the fluid underpressure in the Ibore hole annulus to effect expansion of said cuttermeans; said mandrel having a passage through which fluid pumped down thebore hole annulus can flow upwardly and into the drill string; saidmandrel having flow restricting means in its passage for reducing `thepressure of the fluid flowing upwardly through the mandrel passage; andmeans communicating the low pressure areas of said cylinder and pistonmeans with the reduced pressure region of said mandrel passage.

6. In a rotary drill bit as defined in claim 1; said expanding means forsaid cutter means comprising a mandrel movable within and downwardly ofsaid body, said body and mandrel providing cylinder and piston meanshaving high pressure areas subject to the fluid under pressure in thebore hole annulus to effect expansion of said cutter means.

7. In a rotary drill bit as defined in claim 1; said expanding means forsaid cutter means comprising a mandrel movable longitudinally within andrelative to said body, said body having a cylinder portion, said mandrelhaving a piston portion within said cylinder portion, said portionshaving relatively high pressure areas subject to the fluid underpressure in the bore hole annulus to effect expansion of said cuttermeans.

8. In a rotary drill bit as defined in claim 1; said expanding means forsaid cutter means comprising a mandrel movable longitudinally within andrelative to said body, said body having a cylinder portion, said mandrelhaving a piston portion within said cylinder portion, said portionshaving relatively high pressure areas subject to the fluid underpressure in the bore hole annulus to effect expansion of said cuttermeans; said mandrel having a passage through which fluid pumped down thedrill string annulus can flow upwardly and into the drill string; meansfor reducing the -pressure of the fluid flowing upwardly through themandrel passage; and means communicating the high pressure areas of saidcylinder portion and piston portion with the reduced pressure region ofsaid mandrel passage.

9. In a rotary drill bit adapted for attachment to a drill string to berotated thereby in a bore hole: a main body; cutter means mounted onsaid body for expansion laterally outwardly of said body; a mandrelco-nnectible to the drill string and slidably splined to said body,whereby drilling torque is transmitted from said mandrel to said body;coengageable expander means on said mandrel and cutter means; and fluidoperated means subject to the pressure of fluid in the bore hole annulussurrounding the drill string for elevating said body and cutter meanswith respect to said mandrel to cause said expander means to expand saidcutter means laterally outward.

10. In a rotary `drill bit as defined in claim 9; said fluid operatedmeans comprising a cylinder portion on said body having a cylinder head,a piston portion on said mandrel above said cylinder head and alongwhich said cylinder portion is slidable, the uid under pressure i-n thebore hole annulus acting on said cylinder head to relatively elevatesaid cylinder portion and body along said mandrel.

11. In a rotary drill bit as defined in claim 9; said fluid operatedmeans comprising a cylinder portion on said body having a cylinder head,a pi-ston portion on said mandrel above said cylinder head and alongwhich said cylinder portion is slidable, the fluid under pressure in thebore hole annulus acting on `said cylinder head to relatively elevatesaid cylinder portion and body along said mandrel; said mandrel having apassage through which fluid pumped down the -bore hole annulus can owupwardly into the drill string; and means establishing fluidcommunication between said passage and the region of the cylinderportion located between said cylinder head and piston portion.

12. In a rotary drill bit as delined in claim 9; said uid operated meanscomprising a cylinder portion on said body having a cylinder head, a.piston portion on said mandrel above said cylinder head and along whichsaid cylinder portion is slidable, the fluid under pressure in the borehole annulus acting on said cylinder head to relatively elevate saidcylinder portion and body along said mandrel; said mandrel having apassage through which uid pumped down the bore hole annulus can flowupwardly into the drill string; said mandrel having ow restricting meansin its passage for lreducing the pressure of fluid flowing from Ithebore hole annulus upwardly through the mandrel passage; and meansestablishing fluid communication between said passage above said tlowrestricting means and the region of the cylinder portion located betweensaid cylinder head and piston portion.

13. In a rotary drill bit adapted for attachment to a drill string to berotated thereby in a bore hole: a main body connectible to the drillstring; cutter means mounted on said body for expansion laterallyoutwardly of said body; a mandrel movable longitudinally in said body;coengageable expander means on said mandrel and cutter means; and fluidoperated means subject -to the pressure of iluid in the bor-e holeannulus surrounding the drill string for shifting said mandrellongitudinally in said body and along said cutter means to cause saidexpander means to expand said cutter means laterally outward.

14. In a rotary drill bit as defined in claim 13; said fluid operatedmeans comprising a cylinder portion on said body, a piston portion onsaid mandrel slidable in said cylinder portion, the uid under pressurein the bore hole annulus acting on said piston portion to shift saidmandrel in said body and along said cutter means to expand said cuttermeans.

1S. In a rotary drill bit as delined in claim 13; said fluid operatedmeans comprising a cylinder portion on said body, a piston portion onsaid mandrel slidable in said cylinder portion, said cylinder portionhaving Ian inlet for fluid under pressure in the bore hole annulus toenter said cylinder portion and act on a relatively high pressure sideof said piston portion to shift said mandrel in said body and along saidcutter means -to expand said cutter means.

16. In a rotary drill bit as defined in claim 13; said iluid operatedmeans comprising a cylinder portion on said body, a piston portion onsaid mandrel slidable in said cylinder portion, said cylinder portionhaving an inlet for fluid under pressure in the bore hole annulus t0enter said cylinder portion and `act on a relatively high pressure sideof said piston portion to shift said mandrel in said body and along saidcutter means to expand said cutter means; said mandrel having a passagethrough which fluid pumped down the bore hole annulus can ow upwardlyinto the drill string; and means establishing fluid communicationbetween said passage and the cylinder portion on the low pressure sideof said piston portion.

17. In a rotary drill bit as delined in claim 13; said iluid operatedmeans comprising a cylinder portion on said body, a piston portion onsaid mandrel slidable in said cylinder portion, said cylinder portionhaving an inlet for fluid under pressure in the bore hole annulus toenter said cylinder portion and act on a relatively high pressure sideof said piston portion to shift said mandrel in said body and along saidcutter means to expand said cutter means; said mandrel having a passagethrough which iluid pumped down the bore hole annulus can ilow upwardlyinto the drill string; said mandrel having flow restricting means in itspassage for reducing the pressure of uid flowing from the bore holeannulus upwardly through the mandrel passage; and means establishingfluid communication between said passage above said flow restrictingmeans and the cylinder portion on the low pressure side of said pistonportion.

References Cited UNITED STATES PATENTS 1,805,515 5/1931 Denney 166--55.82,699,921 l/ 1955 Garrison -267 2,859,943 ll/ 1958 Chadderdon 175-269 X3,126,065 3/ 1964 Chadderdon 175-269 DAVID H. BROWN, Primary Examiner.

